Smelting ores or the like



30 bearing iron ores, residues and the like are No Drawing.

Patented Get. 10, 1922.

ihttitti? r tr er...

SMELTING onus on THE LIKE.

T0 allwhomz't may camera: 1

Be it known that I, LUDWIG HErNRroH DIEHL, a subject of Germany,residing in Darmstadt, Germany, have invented certain new and usefulImprovements in smelting ()res or the like (for-which I have filed ap 1in blast-furnaces such as are used in making pig-iron, the metallic zincvolatilized from the charge gives rise to deposits and incrustations inthe throat and gas pipes of the furnace, forming obstructions which attimes cause great trouble. Sometimes the zincfipenetratesinto the jointsof thebrick' work where, becoming gradually oxidized, it increases involume and tends to displace the brick-work. Large quantities of zincavailable which, on account 01" their containing appreciablequantitiesof zinc, or both zinc and sulphur, have hitherto been regarded asunsuitable or even worthless for smelting in blast-furnaces. I

The chief objects oi the present invention are to prepare ,suchzinc-bearing materials in aform chemically and physlcally suitable' fortreatment in the blast-furnace and then by smelting them withsuitableadditionsto separate and recover the iron and zinc without the drawbacksreferred to, substantially the whole of the zinc in the charge beingvolatilized and carried out of the fur nace by the-current of gas as anunobjectionable compound which is recovered as a useful product whilethe iron is tapped ofi' as molten-metal to yield pig-iron or otherferrous product of good quality. According to the invention the rawmaterial employed (viz, the ore, roaster-residue, slagor the like, ormixture of such materials, containing iron and zinc, and hereinaftertermed ore) if it contains sulphur, is first usual reducing and fluxingagents Application filed August 6, 1920. Serial No. 401,819.

desulphurized, and, if it be too fine for blast-furnace work, is broughtinto suitable physical form by sintering, briquetting, or otherwise.Since it must, when charged into the iurnace, contain enough iron toyield molten metal in quantity sufficient to enable the latter to betapped in the usual way, any deficiency in iron is rectified by theaddition of suitable materials, such as iron ore or scrap iron. It isthen smelted in the usual manner in a blast-furnace along with the (coalor coke, limestone and the like) and other materials if desired, and inpresence of a chloride. The presence of a chloride is most easilyprocured by mixing with the charge a chloride in suitable proportions,in which case an alkali chloride, an alkaline earth chloride, zincchloride or a mixture of such chlorides is most suitable, being lesseasily volatile or decomposable at the temperature of the upper part oftheblast furnace than most other chlorides, and being free from metalswhich might pass into the iron produced and impair its quality.v Thezinc present in the charge is thus volatilized,

probably as chloride or oxychloride, and carried out of the furnace by.the gas, while he iron and slagare obtained in a molten condition freeor practically free from zinc. The iron is tapped ofl and may be useddirectly for steel-making, cast into pig-iron, or otherwise utilized.The zinc compound is collected from the gas in any convenient manner; itmay, for example, be recovered partly in the fine dust and partly in thegas washing plant, this method having the advantage that a cleancombustible gas, similar to-ordinary blast-furnace gas and suitable foruse in gas-engines or for heating purposes, may be obtained. The natureand proportions of the fuel, fluxing materials and other additions (ifany) in the charge are chosen with regard to the composition of the oreand kind of iron to be produced, in the manner well understood inordinary blast-furnace practice; by suitable selection of these atypical blast-furnace slag, containing only about 0.1 per cent of zincand adapted to be run of]. in the usual manner, can be obtained.

The quantity of suitable chloride to be added to the charge depends uponthe amount of zinc present and may be in the proportion of about 2 atomsof combined chlorine to 1 atom of zinc present in the ore. I havediscovered, however, thatzinc oxide can be volatilized somewhat readilyalong with zinc chloride if it be heated together with the lattercompound in a current tion of metallic zinc and the troubles indicatedabove would tend toarise in greater or less degree. It is best so toregulate the amount that the zinc product carried out of the furnacecontains little or no metallic zinc; for example the zinc productdeposited in the settling ponds of the gas-washing plant should developtherein only a small amount if any of hydrogen gas.

In smelting the ore with the addition of suitable chloride as described,the formation of incrustations in the furnace and pipes is reduced to aminimum, as the zinc-'Joeing ina more volatile form than heretofore iscarried almost entirely into the flue dust or the gas-washers. Thevolatilized zinc compound while being carried by the gas current isexposed to the action of the lime, alkali and moisture therein; it isalso (EX- posed to the action of alkali in the gaswasherthe water inwhich is normally alkaline and for the purpose of this invention is ifnecessary kept slightly alkaline by the addition of limeor suitablealkali-and the zinc is thus "collected in the wash-water as basiccarbonate or the like, the combined chlorine which was present in thevolatilized compound passing into solution as alkali chloride oralkaline-earth chloride. The crude precipitate, contaminated with cokedust, flue dust and other impurities, may be allowed to, subside in thesettling ponds, collected by filtration or otherwise, washed with waterto remove soluble substances and then calcined to eliminate combustibleand volatile impurities and to renderthe otherwise comparativelyvoluminous product denser. It then consists of crude zinc oxide, whichmay be utilized in any desired manner. y

The solutions of chlorides of the .alkalis or alkaline-earths obtainedin the gas-washing plant can-be evaporated and'the concentrated productused as suitable chloride for fresh operations in the furnace.

The invention is particularly applicable to the treatment of the roasterresidues produced from zinciferous pyrites. As is known, the residueobtained on burning such pyrites in roaster furnaces for the manufactureof sulphuric acid retain a fairly large proportion of sulphur, which maybe into practice.

as much as 5 to 8per cent. I prefer to 'desulphurize, sinter and smeltsuch residues inthe following manner. The residue is crushed to aboutone-quarter inch size and roasted (preferably in rotary kilnsabout 60metresin length by about 2-1; to 3 metres in diameter or in othermechanically-operated furnaces) with fuel and a limited supply of centor less. In order to obtain with a ro-' tary kiln the best results asregards strength of gas, reduction of sulphur contents of the ore andsintering of the latter into a porous material free from dust, thecharge should be heated with a long flame to a final temperature atwhich the material will just begin to fuse and the quantities of fueland air should be such that about one fourth part of the ferric oxide isreduced to ferrous oxide. The desulphurization will then be satisfactoryand the sintering will take place more easilythan on roasting with alarge excess of air. The exit gas can be utilized for the manufacture ofsulphuric acid or otherwise; if desired it can be ren dered richer inE30, by adding a pro-portion of crushed fresh pyrites to the chargebefore the roasting and sintering operation. The desulphurized andsintered product is then smelted with the addition of suitablechlorideas already described, the usual reducing,fiuxing and other additionsbeingmade according to the composition of the ore and the kind ofironrequired.

7 Example.

The following example illustrates the manner in'which the invention maybe put The ore used consisted of zinciferous roaster-residue containing5.02 per cent of sulphur and 41.42 per cent of iron. Thedesulphurization was carriedout in a rotary kiln 60 metres in length and2% metres in diameter having a through-put of about 150 tons of residueper 24 hours. For each metric ton (1000 kiloslof residue there were used65 kilos of coal (containing 66.7 per cent ofcarbon and 1.5 per cent ofsulphur) and 885 cubic metres of air, yielding 910 cubic metres of exitgas containing 3.75 per cent by volume of SO 8.82 per cent of CO and8.06 per cent of 0., The sintered, desulphurized material contained 8.32per cent of zinc, 0.06, per cent of sulphur and 44.21 per cent of iron(31.85 per-cent as Fe O and 12.35 per cent as FeO). The gas leaving thekiln had a temperature in the dust-chamber of 450-500 C. and wassuitable for the manufacture of sulphuric acid. The sintered,desulphurized material was then smelted with the addition of a suitablechloride and reducing, fiuxing and other materials appropriate for theproduction of pig-iron of the quality (in this case, highmanganese iron)desired. Here were used 1308 tons of sintered material, 146 tons of rocksalt (sodium chloride), 2295 tons of coke, 897 tons of limestone, 278tons of scrap iron and 278 tons of iron in the form of manganiferousiron ore containing 75 tons of Mn. There were produced 1046 tons ofpig-iron (containing no zinc, 3.25 per cent Mn, 1.67 per cent Si, 3.68per cent C, 0.038 per cent S, and 0.170 per cent P), 1125 tons of slagcontaining 0.10 per cent of zinc, and 158 tons of flue dust containing21 tons of zinc (existing mainly as oxide, oxychloridc or the like). Thezinc compound carried in the gas was washed out in the gas-washing plantof the furnace; the product was collected from the settling ponds byfiltration, washed, and calcined at a low red heat to drive out combinedwater, carbon dioxide and a small quantity of combined chlorine. It thenweighed 125 tons and contained 66.3

per cent of Zn:82.5 per cent of ZnO. The

flue dust was briquetted and returned to the, furnace. The gas from thewashing plant consisted of good, clean, blast-furnace gas suitable foruse in the ordinary manner.

From the foregoing example it will be seen that the invention affords apractical method of treating roaster-residues so as to effect a cleanseparation of the valuable con- 'stituents thereof, with recovery of theiron, zinc, and (if desired) the sulphur and combustible gas, all in acommercially useful form, and with simultaneous elimination ofblast-furnace slag of the usual type substantially free from zinc.

The invention is also applicable to zinc and iron bearing ores and thelike which are either naturally free from sulphur or are procurable in adesulphurized condition. In such cases if the ore is too fine to becharged directly into the blast-furnace it is first agglomerated orbriquetted in any suitable manner and if necessary any deficiency iniron is made goodas already indicated. It is then smelted with the aidof suitable chloride and other additions as hereinbefore described.

Having thus fully described the nature of the said invention and thebest means I know of carrying the same into practical effeet, I claim 1.The treatment of zinciferous iron ores or the like adapted to be smeltedin a blast furnace to obtain pig-iron, which treatment consists insmelting the ore in a blast furnace in presence of a chloride along withthe appropriate fiuxing and other ingredients of a blast-furnace charge,tapping ofi the molten iron produced and collecting the volatilizedZinciferous material carried out of the furnace by the gases.

2. The treatment of zinciferous iron ores or the like adapted to besmelted in a blast furnace to obtain pig-iron, which treatment consistsin smelting the ore in a blast-furnace in presence of a chloride alongwith the appropriate fluxing and other ingredients of a blast-furnacecharge, tapping off the molten iron produced, collecting by means ofalkaline wash-water the volatilized zinciferous material carried out ofthe furnace by the gases, and washing and calcining the zinciferousproduct.

3. The treatment of Zinciferous iron ores or the like adapted to besmelted in a blast furnace to obtain pig-iron, which treatment consistsin agglomerating them into a form suitable for blast-furnace practice,smelting them in a blast-furnace in presence of a chloride along withthe appropriate fluxing and other ingredients of a blast-furnace charge,tapping off the molten iron produced and collecting the volatilizedzinciferous material carried out of the furnace by the gases.

4. The treatment of zinciferous iron ores or the like adapted to besmelted in a blast furnace to obtain pig-iron, which treatment consistsin agglomerating them into a form suitable for blast-furnace practice,smelting them in a blast-furnace in presence of a chloride along withthe appropriate fluxing and other ingredients of a blast-furnace charge,tapping off the molten iron pro duced, collecting by means of alkalinewashwater the volatilized zinciferous material carried out of thefurnace by the gases, and washing and calcining the zinciferous product.

5. A nrocess of winning zinc compounds from sulphur-free zinciferous andferruginous ores or the like, which consists in volatilizing the Zinc asa compound by smelting the ore in a blast furnace in presence of achloride and collecting the zinciferous material carried out of thefurnace by the gases.

in testimony whereof I have signed my name to this specification.

LUDNIG HEINRICH DIEIUL.

